1. Field of the Invention
The present invention relates to a seat belt retracting and winding device of the type in which a seat belt may be automatically retracted and wound on a winding reel under restoring or unwinding spring force of spiral springs, and more particularly to a seat belt retracting and winding device which may exert a reduced retracting and winding force to the seat belt after it has been fastened across the vehicle occupant.
2. Brief Description of Prior Art
There have conventionally been known seat belt retracting and winding devices which contain only one spiral spring having its one end attached to a shaft of a winding reel and the other end attached to the body of a retractor. In these devices, when the seat belt is paid out and thus the winding reel is rotated, the spiral spring is wound to exert an unwinding or restoring spring force to the seat belt, thereby retracting and winding the latter onto the winding reel. Generally the spiral spring used in these devices exerts an increased unwinding spring force to the seat belt according to the increase in length of the seat belt paid out. Therefore, when the seat belt is paid out in larger length and fastened across the occupant, the winding spring force of the spiral spring exerts a large restraining or tightening force to the seat belt. Such large restraining force not only brings about an uncomfortable feeling to the occupant but also prevents his smooth movement. In cases where the large restraining force is exerted to the driver, the movement of the driver is restricted so that the safe driving operations will be adversely affected.
In the conventional devices of the type in which a lap belt and a shoulder belt are made of a continuous webbing and winding means is disposed on the shoulder belt side, it is necessary to pay out the seat belt in particularly larger length, so that the restraining force exerted to the occupant becomes very large. Further, in a passive seat belt system in which the length of the seat belt paid out is further increased, the occupant experiences much more uncomfortable restraining force.
In the seat belt retracting and winding devices of the type described, it is desirable to reduce the unwinding spring force of the spiral spring in order that the restraining force exerted to the occupant may be reduced. However, the reduced spring force brings about a disadvantage such that the seat belt is not completely retracted and wound on the winding reel when the seat belt is unfastened or released.